wp_untrash_comment( int|WP_Comment $comment_id )

function wp_untrash_comment($comment_id) {
	$comment = get_comment( $comment_id );
	if ( ! $comment ) {
		return false;
	}

	/**
	 * Fires immediately before a comment is restored from the Trash.
	 *
	 * @since WP-2.9.0
	 * @since WP-4.9.0 Added the `$comment` parameter.
	 *
	 * @param int        $comment_id The comment ID.
	 * @param WP_Comment $comment    The comment to be untrashed.
	 */
	do_action( 'untrash_comment', $comment->comment_ID, $comment );

	$status = (string) get_comment_meta( $comment->comment_ID, '_wp_trash_meta_status', true );
	if ( empty($status) )
		$status = '0';

	if ( wp_set_comment_status( $comment, $status ) ) {
		delete_comment_meta( $comment->comment_ID, '_wp_trash_meta_time' );
		delete_comment_meta( $comment->comment_ID, '_wp_trash_meta_status' );
		/**
		 * Fires immediately after a comment is restored from the Trash.
		 *
		 * @since WP-2.9.0
		 * @since WP-4.9.0 Added the `$comment` parameter.
		 *
		 * @param int        $comment_id The comment ID.
		 * @param WP_Comment $comment    The untrashed comment.
		 */
		do_action( 'untrashed_comment', $comment->comment_ID, $comment );
		return true;
	}

	return false;
}